ST EVALSTPM32, Руководство пользователя, Страница: 6 / 15

2.1.6 On-board USB (UART) connection
UART peripheral can be selected to communicate with the device. In this case, all SW1 switches should be in ON
position when the device powers up. USB port is isolated from the board through STISO621 transceiver to safely
connect the board to PC. UART isolated pins are also available on J2 connector for MCU connection or debug
purpose. If UART connection is used, a separate 3.3 V DC must be provided to UART section.
For the board version 1 only: UART peripheral also communicates to the device. In this case, all SW1 switches
should be in ON position when the device powers up. RS232 port is isolated from the board through Si8621
transceiver to safely connect the board to PC; in this case, J3 jumper must be connected. UART isolated pins
are also available on J2 connector for MCU connection; in this case J3 jumper must be disconnected. If UART
connection is used, a separate 3.3 V DC must be provided to UART section.
Table 5. J2 UART connector
Name Description
1 Master TXD – Device RXD (Data to STPM)
2 Master RXD – Device TXD (Data from STPM)
3 +3.3 V DC
4 GND
2.1.7 Metrology
Current sensing is performed by CT or shunt, while voltage is sensed by voltage dividers.
The EVALSTPM34 board has two currents and two voltage channels, while the EVALSTPM33 has two currents
and one voltage channel and the EVALSTPM32 has one current and one voltage channel available. Main design
parameters are listed in the below table.
Table 6. EVALSTPM3x evaluation board parameters
Channel Parameter Value
Primary current
Current sensor sensitivity k
S
(1)
2.4 mV/A
Shunt sensor sensitivity
(2) 0.3 mV/A
Primary voltage
R
1
voltage divider upper resistor
(3)
810000 Ω
R
2
voltage divider upper resistor
470 Ω
Secondary current (4)
k
S
current sensor sensitivity
2.4 mV/A
Secondary voltage
R1 voltage divider upper resistor 81000 Ω
R2 voltage divider upper resistor 470 Ω
Any
C
P
constant pulse
41600 pulses/kWh
1. For the EVALSTPM34 board only.
2. For the EVALSTPM32 and EVALSTPM33 board only.
3. R1, R2 names do not refer to specific resistors on the schematic, but these names indicate voltage divider resistors.
4. For the EVALSTPM34 and EVALSTPM33 board.
A 22 nF capacitor in parallel with R2 implements an antialiasing filter for voltage signal. Regarding to current
signal, the antialiasing filter is given by a 10 nF capacitor and 2 x 1 KOhm resistors.
2.1.8 LED
Two LEDs are connected to programmable LED pins of the device.
2.1.9 Clock
Clocking is provided to the board through 16 MHz quartz. 1 MOhm resistor and 15 pF capacitors are used to filter
noise.
UM1748
Board description
UM1748 - Rev 3
page 6/15